We designed this study to assess whether bivalirudin is superior to unfractioned heparin + protamine in patients undergoing PCI. All patients older than 18 years of age, who require coronary angiography for suspected or established coronary artery disease, but without ST-segment changes, will receive a loading dose of 600 mg clopidogrel at least 2 hours prior to the procedure. Eligible patients who do not meet the exclusion criteria and in whom angiography reveals that revascularization is required and the target lesion(s) is (are) amenable to PCI, will be randomized to receive a bolus of 140 U/kg of heparin or bivalirudin to be administered as an intravenous bolus of 0.75 mg/kg prior to the start of the intervention, followed by infusion of 1.75 mg/kg per hour for the duration of the procedure. All patients will receive aspirin indefinitely and clopidogrel for at least 1 month after PTCA or implantation of bare metal stents and for at least 6 months after implantation of drug-eluting stents; clopidogrel treatment for more than 6 months will be encouraged.19 The primary end point of the study is in-hospital major bleeding. The study is designed to show whether bivalirudin is superior to UFH + protamine with respect to the primary end point.